The rise of the Second Amendment as a serious obstacle to gun control legislation is astonishingly recent.

It is a tribute less to the Founding Fathers than to the power of the contemporary gun-rights movement, which has not only exerted disproportionate influence on Congress, but also helped transform the landscape of constitutional argument.

We should be able to have a serious national discussion uninhibited by wild claims about the meaning of the Constitution.

Here's a quick way to see how rapidly things have changed.

Warren Burger was a conservative Republican, appointed chief justice by President Richard Nixon in 1969. In a speech in 1992, six years after his retirement, Burger declared that "the Second Amendment doesn't guarantee the right to have firearms at all."

In his view, the purpose of the Second Amendment was only "to ensure that the state armies' -- the militia -- would be maintained for the defense of the state."

A year before, Burger went further. On "MacNeil/Lehrer NewsHour," Burger said the Second Amendment "has been the subject of one of the greatest pieces of fraud -- I repeat the word 'fraud' -- on the American public by special interest groups that I have ever seen."

To understand what Burger was thinking, consider the words of the Second Amendment: "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."

Fair-minded readers have to acknowledge that the text is ambiguous. Sure, it could fairly be read to support an individual right to have guns. But in light of the preamble, with its reference to a well-regulated militia, it could also be read not to confer an individual right, but to protect federalism, by ensuring that the new national government wouldn't interfere with citizen militias at the state level.

A lot of historians believe, with Burger, that some version of the latter interpretation is the right one. Until remarkably recently, almost all federal judges have agreed. It is striking that before its 2008 decision in District of Columbia v. Heller, the Supreme Court had never held that the Second Amendment protects an individual right to have guns.

For almost seven decades, the court's leading decision was U.S. vs. Miller. The 1939 case involved a ban on possession of a sawed-off shotgun. Sounding like Burger, the court unanimously said that the Second Amendment's "obvious purpose" was "to assure the continuation and render possible the effectiveness of" the militia. Without evidence that a sawed-off shotgun was related to preservation of a well-regulated militia, the court refused to say that the Second Amendment protected the right to have such a weapon.

For decades, federal courts overwhelmingly rejected the conclusion that the Second Amendment protects an individual right. It wasn't until the 21st century that lower federal courts, filled with appointees of Presidents Ronald Reagan and George H.W. Bush, started to adopt the individual-rights position. And, of course, the Supreme Court itself adopted that view in 2008, by a 5-to-4 vote.

I am not saying that the court was wrong. The legal question is genuinely difficult, and people disagree in good faith how to solve it. What is important to see is that in the very recent past, the U.S. has lived through a Second Amendment revolution, spurred by an intensely focused and well-funded social movement with both legal and political arms.

More important still, the Supreme Court has proceeded cautiously, refusing to shut the door to all gun regulation. On the contrary, the court said, "Nothing in our opinion should be taken to cast doubt on longstanding prohibitions on the possession of firearms by felons and the mentally ill, or laws forbidding the carrying of firearms in sensitive places such as schools and government buildings, or laws imposing conditions and qualifications on the commercial sale of arms."

To this the court added that the sorts of weapons it was protecting were those "in common use at the time" that the Second Amendment was ratified. We should respect the fact that the individual right to have guns has been established, but a lot of gun-control legislation, imaginable or proposed, would be perfectly consistent with the court's rulings.

In the political arena, opponents of gun control, armed with organization and money, have invoked the Second Amendment far more recklessly, treating it as a firm obstacle to any effort to regulate guns and bullets.

As a result, they have made it difficult for Congress, and many state legislatures, even to hold serious discussions about what sorts of regulation might save lives. Consider this disturbing statement by Stephen Halbrook, a lawyer who has represented the National Rifle Association, about the very kinds of guns used in the Connecticut tragedy: "They get a lot of coverage when there's a tragedy, but the number of people unlawfully killed with them is small."

Reasonable people can debate about what policies would actually work. That is a debate worth having. It is past time to stop using the Second Amendment itself as a loaded weapon, threatening elected representatives who ought to be doing their jobs.

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Cass R. Sunstein is the Felix Frankfurter professor of law at Harvard University.